I have created a simple scene in EFPSE 1.5 PRO version (not LITE and NOT experimental), which was installed from scratch. I used vanilla weapon and ammo items, but the problem is still present. Maybe it is a hardware rather than software specific problem.
I doubt it. I'll ask you to check it after the update is here. I had some changes in save system since last update so it might just be fixed already, just not here yet.